Improvement in photo-mechanical printing



UNITED STATES PATENT OFFIG'E.

THOMAS C. ROCHE, OF BROOKLYN, ASSIGNOB TO E. & H. T. ANTHOIW Y 85 (30.,

OF NEW YORK, N. Y.

IMPROVEMENT IN PHOTO-MECHANICAL PRINTING.

Specification forming part of Letters Patent No. 218,137, dated August5, 1879; application filed December 13, 1878.

To all whom it may concern Be it known that I, THOMAS G. ROCHE, of thecity of Brooklyn, county of Kings, and State of New York, have made andinvented an Improvement in the Art of Photo-Mechanical Printing, ofwhich the following is a specification.

My invention consists,' essentially, in the methods hereinaftermentioned and described of constructing and preparing the gelatine filmemployed for the reception of the photographic image or impression, andwhich, together with a supporting-plate having special features adaptedto hold and retain the film firmly in place, is eventually used to printfrom in fatty inks, after the mannerof lithography.

The first requisite to the greatest attainable perfection in this artafter a clear and strong negative has been obtained is a gelatiue typeor film having those chemical and structural characteristics which willenable it to receive and retain in the most perfect manner the .actinicimage conveyed to it through the negative, with all the delicategradations of light and shade found in the natural object, together withthat firmness, smoothness of surface, and adhesiveness to the plate ortablet on which it is placed that will enable it to endure withoutinjury or disturbance the application of ink of any desired consistencyor stiffness and the pressure necessary to secure a complete transfer ofthe picture in the printmg. i

The main object of my improvement, therefore, is to secure withuniformity and certainty all the conditions essential to success; and tothis end I have discovered that the requisite hardness, firmness,fineness of structure, and smoothness of surface may be secured in thegelatine film forming the photographically-impressed printing-surface,and also the necessary degree of toughness and elasticity, by theapplication during its preparation of alcohol previously heated to adegree of temperature nearly coincident with that of the gelatinesolution, either before or after the application of the sensitizingagent employed.

I have also discovered that plates of metal, glass, or other materialcapable of abrasion,

when out or roughened by the process known as the sand blast, ascontradis'tinguished from the more common methods of grinding orroughening by mechanical means with emery, or sand and water, orchemically by means of an acid bath, meet more adequately the conditionsnecessary to the procurement and production of the best effects inphoto-mechanical printing, and which depend so greatly on the intimateunion of the printing-film and its supporting plate or tablet, andespecially the degree of tenacity with which the former is held to thelatter.

This result may be due to the fact that the sand-blast treated plate orsurface consists of pits, excavations, and under-cuts, into which thematerial of the film flows and becomes clinched, as it were, suchcondition serving to hold said film so firmly and tenaciously in placethat it cannot be removed or torn away from its support when beingprinted from in any kind of press, and using ink of any desiredthickness or consistency.

I will now proceed to describe more particularly and in detail myimproved method of preparing the gelatine film previous to its beingflowed upon its supporting-plate. I first take fine gel atine, say aboutthree hundred and sixty grains, and immerse it in pure cold water untilit has absorbed or taken up all of the liquid it will. I then pour offthe surplus water, and dissolve the gelatine by the application of heat,a sand or water bath being the preferable way. I then dissolve, say, onedram of biehromate of ammonia or potash in about one ounce of water, andadd this to the gelatine solution, keeping the same warm, preferably ata temperature of not less than 90 Fahrenheit nor higher than 150Fahrenheit. I then take about six ounces of alcohol and dilute it withfrom one and a half to two ounces of pure water. Now, were the alcohol,diluted or not, added in its cold state to the gelatine solution, itwould coagulate the same, the coagululn presenting itself as a curd-likeor ropy substance, separated from the more fluid portion of thesolution, thereby rendering it entirely unfit for its intended purpose.To avoid this coagulation, therefore, I beat the alcohol previous toadding it to and mixing it with the gelatine solution, the relativetemperatures being about 110 Fahrenheit for the Fahrenheit. When dry,unless the plate has been dried on a leveling-stand, and therealcoholand Fahrenheit for the gelatine l byafilmot'sufiicientthicknesshasbeenformed,

at the time of mixing the same together.

If undiluted alcohol should be used, it

would produce partial coagulation even at a temperature of Fahrenheit.with the gelatine solution heated to Fahrenheit; but if heated only toits boiling-poilit-namely, 174 Fahrenheit-then coagulation of thegelatine is prevented. Still this method of using the alcohol isobjectionable, both because of the loss of the spirit by rapidevaporation at that temperature and because the gelatine solution towhich it might be added would dry too rapidly, and thereby injure thestructural condition of the him. The better method, accordingly, is todilute the alcohol in the proportion of from one-third to one-fourthwater, heating the solutions separately up to about the degrees oftemperature first stated, and then adding them together in their heat-edcondition.

The proportions of the gelatine and bichromate or alcohol maybe somewhatvaried without material change, but the propoltion of the dilutedalcohol should not, preferably, be reduced below one-fourth, by weight,to about three-fourths of the gelatine and bichromate combined.

The mixture should be well stirred as the heated alcohol is added, andthen the whole filtered, for which purpose a flannel cloth laid in afunnel may be used, and the filtering done while the mixture is beingpoured into the bottle in which it is to be kept for use. Preferably Iuse a funnel that extends to the bottom of the bottle, to avoid theformation of air-bubbles in the mixture, which, when once formed, aresomewhat ditlicnlt to suppress, it being important that they shall notappear on the plate when the mixture is flowed onto it.

I prefer, also, not to allow the temperature of the solution to fallbelow, say, 130 Fahrenheit before it is applied to the plate, and tothis end it may be kept in a sand oi water bath of the proper degree ofheat.

A gelatine solution thus made, when flowed onto a plate, will form afine, hard, and tough film, tenaciously adherent to the plate, andpresenting a fine, smooth, and glossy surface for the reception of thephotographic impresslon.

This solution is applied in a heated state by flowing the same over aplate having a roughened surface of the character before described,which is also preferably heated to about the same temperature as thesolution, so as to cover its surface thoroughly and allow the materialof the film to enter completely into all the pits, excavations, andunder-cuts of the plate, any surplus being then drained off. The plate,with the film on it, is then dried in a heated oven or by other suitablemeans, the heat applied to dry it preferably not to be greater than 120,nor less than a second coat of the gelatine mixture is preferblyapplied, drawing oh the surplus from the opposite edge or corner fromthat from which the first flowing was drained. This second coat is driedlike the first, the operation of drying in the oven being continueduntil vapor ceases to rise from the film.

The sensitized solution should, of course, be protected from actiniceffect, and the operation of coating the plate be carried on in theabsence of actinic light.

It may be stated, incidentally, that the sensitizing agent may beapplied to the gelatine solution either before or after the applicationof the heated alcohol, and may even be applied to the plate after thegelatine film has been formed upon it with equal effect, and withoutdeparting from the spirit of my invention.

The plates prepared as hereinbefore described, like the gclatinesolution when sensitized, must be kept from the effect of actinic light,but may be exposed at any time within ten or twelve days from theirpreparation with a negative for the reception of the photographic image.

After the plate has been exposed it is freed from all bichromate notacted on by the light, which may be done by washing in cold runningwater for a short time, and then as a matter of preference allowing itto dry, after which it is ready for the printing-press.

Now, 1 am aware that alcohol in a cold state has been mixed withgelatine to form a varnish or preservative coating for pictures and forother purposes.

I am also aware that alcohol in such state has been mixed and used invery small quantity with a sensitized gelatinesolution, together with ahardening element-such as tannin and other in gredients-the wholecompounded and intermixed by the application of heat to produce aphotographic printing-film, from which to print in fatty inks; but I amnot aware of alcohol being used previous to my invention, heatedpreviously to its admixture with such solufion, with or without theaddition of a bichromate or other sensitizing agent nearly up to thesame degree of temperature, for the twofold purpose of preventing thecoagulation of the gelatine and also hardening the same, thus taking theplace of and dispensing with the ingredients usually employed, andespecially alum, or, as well known, the effect produced by the exposureof the film to light for the purpose of enabling itto withstand thepressure of printing.

I am also aware that glass and metal plates upon which to paint or printin the making of signs have been roughened mechanically in the ordinaryway, or chemically by immersion in an acidbath; also, that a glass plateso roughened has been used as a support for a sensitized film ofordinary character; but such I do not claim, broadly, as I havediscovered that no means for roughening the film-supporting tabletprevious to the employment of the well-known sand-blast process by mehave been found sufiicient to produce the necessary and peculiarconstruction of tooth required for holding, writing, and securing thefilm to the plate with sufficient tenacity to admit of the use of athick ink in the printing of proofs.

'Havin g thus described my invention, what I claim as new, and desire tosecure by Letters Patent, is

,l. The described process of producing and preparing gelatine films foruse in the production of plates for photographic printing in fatty inks,which consists essentially in first immersing the gelatine in cold waterand allowing it to absorb as much of the same as it will, then dissolvingthe gelatine by heat in the usual way, then taking alcohol diluted withabout one-fourth to onethird its volume of water and heating it towithin afew degrees of the temperature of the gelatine solution andfinally uniting and mixing the alcoholic and gelatine solutions togetherwhile in their relativelyheated state, substantially as and for thepurpose specified.

2. lhe described process of producing and preparing gelatine films foruse in the production of plates for photographic printing in fatty inks,which consists essentially in first immersingthe gelatine in cold waterand allowing it to absorb as much of the same as it will, thendissolving the gelatine by heat in the usual way, then adding to thegelatine solution while hot a solution of bichromate of ammonia orpotash or other suitable sensitizing agent, then taking alcohol dilutedwith about one-fourth to one-third its volume of water and heating it towithin a few degrees of the temperature of the sensitized gelatinesolution, and finally uniting and mixing the alcoholic and sensitizedgelatine solutions together in their relatively-heated state, allsubstantially as and for the purpose set forth.

3. In combination with a gelatine film compounded and preparedsubstantially in the manner above described and claimed, a supportingplate or tablet of metal, glass, or other hard substance susceptible ofabrasion, having a sand-blast roughened surface for holding the filmfirmly and with such tenacity as to permit of the use of ink of anydesired consistency in printing, the whole forming an improvedphotocollotype or photographically impressed and prepared plate forprinting from in fatty inks after the manner of lithography,substantially as and for the purpose specified.

THOMAS C. ROCHE.

Witnesses:

B. G. CLARK, M. F. CLIFTON.

